These structural arms are generally made of titanium owing to the high resistance of this substance. However, so as to reduce the weight of these arms, it has been considered to make them from a composite material. Now, the diameters of turbojet engine casings, especially currently studied double-flow casings, are so large that a large number of problems are posed concerning the resistance of these composite material arms, the transmission of stresses by these arms over a significant distance length, as well as the linking of these arms, namely first with the metallic hub of the casing and secondly with the external ferrule, which is also metallic.
European patent EP-A-O 274 293 has already described a double flow turbo-engine inlet casing comprising a set of arms made of a composite material disposed radially, each of them comprising a metallic tie rod forming the central core of this arm. The tie rod is fixed between the external ferrule and the internal hub and is prestressed via the tightening of a nut. Accordingly, the hub is a floating type hub and is borne by said radial tie rods. However, this type of device does not reduce the overall weight of the casing since the weight gain obtained by the use of the composite material is compensated by the relatively heavy metallic tie rod.
Patent application FR-A-2 522 362 also describes the mounting elements provided on one internal casing and on one external casing and fitted with housings intended to respectively receive one of the two extremities of a vane. These mounting elements make it possible to instal and remove a vane separately and elastically support these vanes.
Finally, the patent application FR-A-2 610 673 also describes a multiflow turbojet engine with an external blowing rectifier ring and comprising a stage of vanes with fixed rectifiers without a platform and regularly disposed between one internal ring and one external ring. These internal and external rings have a set of notches allowing for fixing the two extremities of the vanes of the rectifier.
The two devices described above complicate the construction of the casing and require the addition of mounting elements. Thus further increasing the overall weight of the casing.